Exposure assessment and heart rate variability monitoring in workers handling titanium dioxide particles: a pilot study
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Titanium dioxide (TiO2) particles are used for surface coating and in a variety of products such as inks, fibers, food, and cosmetics. The present study investigated possible respiratory and cardiovascular effects of TiO2 particles in workers exposed to this particle at high concentration in a factory in China. The diameter of particles collected on filters was measured by scanning electron microscopy. Real-time size-dependent particle number concentration was monitored in the nostrils of four workers using condensation particle counter and optical particle counter. Electrocardiogram was recorded using Holter monitors for the same four workers to record heart rate variability. Sixteen workers underwent assessment of the respiratory and cardiovascular systems. Mass-based individual exposure levels were also measured with personal cascade impactors. The primary particle diameter ranged from 46 to 562 nm. Analysis of covariance of the pooled data of the four workers showed that number of particles with a diameter <300 nm was associated positively with total number of N–N and negatively with total number of increase or decrease in successive RR intervals greater than 50 ms (RR50+/−) or percentage of RR 50+/− that were parameters of parasympathetic function. The total mass concentration was 9.58–30.8 mg/m3 during work, but significantly less before work (0.36 mg/m3). The clear abnormality in respiratory function was not observed in sixteen workers who had worked for 10 months to 13 years in the factory. The study showed that exposure to particles with a diameter <300 nm might affect HRV in workers handling TiO2 particles. The results highlight the need to investigate the possible impact of exposure to nano-scaled particles on the autonomic nervous system.
KeywordsTitanium dioxide Heart rate variability Nanoparticles Nanomaterial exposure Health and environmental effects
The authors thank Prof. Andrew D. Maynard, from the Department of Environmental Health Sciences, University of Michigan, School of Public Health, Ann Arbor, Michigan, USA, and Dr. Charles Geraci, National Institute for Occupational Health and Safety, Cincinnati, Ohio, USA for the generous advice on the use of the CPC and OPC in parallel for the measurement of nano-scaled particles. This study was supported in part by grants from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (NEXT Program #LS059) and Japan Society for the Promotion of Science (JSPS) Grants-in aid for Scientific Research #26305023) and Sasagawa China-Japan Medical Association.
S.I., S.O., Y.F., Y.H., N.H., T.K., and G.I. conducted exposure assessment. W.L., Y.L., Q.W., and X.D. conducted health examination. K.W. analyzed and interpreted the data. S.O., Y.F., and T.K. conducted characterization of particles. G.I., T.K., and S.I designed the study. S.I. drafted the manuscript. G.I. and T.K. revised it critically for important intellectual content. All authors approved the final version of the manuscript.
Compliance with ethical standards
Conflict of interest
All of the authors declare that there are no competing interests including source of direct and indirect support.
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